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smartkey warning

Discussion in 'Gen 2 Prius Main Forum' started by frossie, Oct 26, 2007.

  1. frossie

    frossie New Member

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    So I am reading the manual for our Prius and it says all in bold:

    Now, I generally follow warnings :p but I like to know why they say never to leave the keys inside. Aside from the obvious property risk (somebody can drive off!), is there a technical reason why you should not do this, and how (if at all) does it link to the previous statement about registering the key?
     
    #1 frossie, Oct 26, 2007
  2. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    The only thing I can think of is that perhaps the SS/SK system and the fob are chattering back and forth all the time which could discharge the 12v.
    It's a stretch, but that's the only downside I can think of other than theft.
     
    #2 TonyPSchaefer, Oct 26, 2007
  3. RobH

    RobH Senior Member

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    I don't think the manual writer quite understood the key system.

    The transponder is an unpowered device that can only be detected when placed in the keyslot. It's embedded inside the keyfob, but is independent of the SKS and remote button functions. Registering the transponder code is one of the two steps in linking a keyfob to the car.

    Registering the SKS/remote security code is the second step in linking a keyfob to the car. It is possible to have only one of these two registrations, in which case the other can not be used to lock/unlock the car. There are many tales about used keyfobs that can have their transponder code registered, but not the SKS/remote code.

    The reason that you don't want to leave a SKS/smart keyfob inside the car (besides any security concerns) is that there are repeated communications between the car computer and the keyfob. It's enough of a power consumption for the car that they actually slow down the repeat rate after several days in order to conserve the car battery. Every time the keyfob receives a message from the car, it has to reply with its security code. Transmitting the security code consumes significant power from the keyfob battery.

    If you want to leave the keyfob inside the car, you can avoid the battery issues by disabling the SKS system with the switch on the dash, just below the steering column. This is also a good idea when you leave the car inactive for several days. I'm not certain, but I think I recall that the car actually stops polling for the keyfob after several weeks. So you may need to use the remote button or mechanical key if the car has been idle for a long time. Once you unlock the car (or maybe you have to get all the way to READY mode), the polling returns to normal and the SKS function should resume function.
     
    #3 RobH, Oct 26, 2007
  4. frossie

    frossie New Member

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    <div class='quotetop'>QUOTE(RobH @ Oct 25 2007, 11:17 PM) [snapback]530628[/snapback]</div>
    Thanks Rob. If that's the case, I don't have a problem with that at all, I just hate the phrasing. In my mind "Never" is reserved for stuff that is dangerous to people or equipment (like, "Never put a rear facing childseat in the front passenger seat"). I take "Never" extremely seriously :D What it sounds like it should have said is "Don't leave the keyfob in the car, because if you do it will drain your battery a lot faster".

    It all comes down to me waking up in the middle of the night thinking "Hey, I left my handbag with the fob in the car" - "Never" means rush down to the garage and get it out NOW - "Don't/Shouldn't" means I can give myself a kick for it and go back to sleep.

    Ok, so call me a pedant. I deserve it.
     
    #4 frossie, Oct 26, 2007
  5. firepa63

    firepa63 Former Prius Owner

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    Leaving the fob inside the car will run down the 12 volt battery as the fob and computer will continuously "talk" to each other. Although this is not a high load, it will definitely have an impact on how long you can leave the car without starting it up.
     
    #5 firepa63, Oct 26, 2007
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